Does transcranial direct current stimulation during writing alleviate upper limb freezing in people with Parkinson’s disease? A pilot study

Transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) can boost motor performance in Parkinson’s disease (PD) when it is applied at rest. However, the potential supplementary therapeutic effect of the concurrent application of tDCS during the training of motor tasks is largely unknown. The present study examined the effects of tDCS on upper limb motor blocks during a freezing-provoking writing task (the funnel task) requiring up- and down-stroke movements at alternating amplitudes. Ten PD patients and 10 age-matched controls underwent two sessions of writing combined with 20 min of anodal or sham tDCS on the left M1 in a randomized cross-over design. The primary outcome was the number of upper limb freezing episodes during five trials of the funnel task on a touch-sensitive tablet. PD patients showed a significant reduction in freezing episodes during tDCS compared to sham. No effects of tDCS were found for the amplitude, variability and speed of the strokes outside the freezing episodes. However, patients who reported freezing episodes in daily life (N = 6) showed a beneficial effect of tDCS on stroke characteristics. These results indicate a subgroup-dependent variability in response to non-invasive brain stimulation applied during the performance of motor tasks in PD. This warrants future studies to examine tDCS as an adjuvant tool for training programs aimed to reduce motor deficits related to freezing.     

重复经颅磁刺激对轻度认知障碍的干预效果

轻度认知障碍(mild cognitive impairment, MCI)是介于正常认知老化和老年痴呆的中间状态, 目前尚无有效的药物治疗方案。重复经颅磁刺激(repetitive transcranial magnetic stimulation, rTMS)可通过诱导突触可塑性的改变来改善大脑的认知功能。对rTMS干预MCI认知功能的有效性及神经机制进行分析。未来研究应优化定位手段, 延长对干预效果的随访评估, 考察不同刺激参数和刺激靶区对干预有效性的影响, 以及结合脑成像技术来探索rTMS的干预机制。     

Magnetic stimulation studies of foveal representation

The right and left visual fields each project to the contralateral cerebral hemispheres, but the extent of the functional overlap of the two hemifields along the vertical meridian is still under debate. After presenting the spatial, temporal, and functional specifications of Transcranial Magnetic Stimulation (TMS), we show that TMS is particularly suitable to study the question of foveal representation as it allows one to study the effects of selective disruption of left or right hemisphere functions on the processing of centrally presented stimuli. Future strategies for the use of TMS in further tests of visual word recognition are suggested.     

成年雄性斑胸草雀高级发声中枢鸣声控制的右侧优势

鸣禽是研究语言功能的动物模型。鸣禽端脑的高级发声中枢(high vocal center, HVC)与人类布洛卡氏区具有功能同源性。利用电损毁与声谱分析相结合的方法, 对成年雄性斑胸草雀两侧HVC分别进行电损毁, 观察HVC控制鸣声的侧别差异。结果表明, 损毁左侧HVC对长鸣和鸣曲的频域和声强特征均无显著性影响。损毁右侧HVC导致长鸣的振幅、调频、幅度调制显著减小(p < 0.05), 鸣曲的振幅、平均频率、峰频率显著减小(p < 0.05)。损毁双侧HVC后均引起鸣曲时域特征的改变, 暗示鸣曲时域特征的编码需要两侧半球鸣唱系统的整合。HVC在控制鸣声频域和声强特征上具有右侧优势, 但对鸣曲时域特征的控制需要两侧HVC的共同参与。